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   <title>Zoltan User's Guide:  Jostle Interface</title>

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<div align=right><b><i><a href="ug.html">Zoltan User's Guide</a>&nbsp;
|&nbsp; <a href="ug_alg_hier.html">Next</a>&nbsp; |&nbsp; <a href="ug_alg_parmetis.html">Previous</a></i></b></div>

<h2>
<a NAME="Jostle"></a>Graph partitioning: Jostle</h2>
<a href="https://staffweb.cms.gre.ac.uk/~c.walshaw/jostle/">Jostle</a> is a library for graph
(mesh) partitioning and load balancing developed at the University of Greenwich,
London, UK, by Chris Walshaw [<a href="ug_refs.html#jostle">Jostle</a>,
<a href="ug_refs.html#walshaw">Walshaw</a>].
The parallel version of Jostle is sometimes called pjostle. In the Zoltan
context, the name Jostle always refers to the parallel version of the library.
The main algorithm used in Jostle is based on multilevel graph partitioning,
and a diffusion-type method is available for repartitioning. Hence the
Jostle library is very similar to ParMETIS. See the <a href="ug_alg_parmetis.html">ParMETIS</a>
section for a brief description of graph partitioning as a model for load
balancing.
<p>At present, only the most common Jostle options are supported by Zoltan.
These are briefly described below. For further details, see the documentation
available from the <a href="https://staffweb.cms.gre.ac.uk/~c.walshaw/jostle/">Jostle home page</a>.
Other options may be added to Zoltan upon request.
<p>Note that Jostle is not distributed with Zoltan. If you wish to use
Jostle within Zoltan, you must first obtain a license for Parallel Jostle
and install it on your system. The license is currently free for academic
use.&nbsp; Zoltan has been tested only with parallel Jostle version
1.2.* and may be incompatible with other versions.
Zoltan offers only limited support for Jostle and this may be
discontinued in the future.
<br>
<table WIDTH="100%" NOSAVE >
<tr>
<td VALIGN=TOP><b>Value of LB_METHOD:</b></td>
<td><b>GRAPH</b></td>
</tr>
<tr>
<td VALIGN=TOP><b>Value of GRAPH_PACKAGE:</b></td>
<td><b>Jostle</b></td>
</tr>

<tr>
<td><b>Parameters:</b></td>

<td></td>
</tr>

<tr>
<td VALIGN=TOP>&nbsp;&nbsp;&nbsp; <i>JOSTLE_OUTPUT_LEVEL</i></td>

<td>Amount of output Jostle should produce.&nbsp; (integer)</td>
</tr>

<tr>
<td VALIGN=TOP>&nbsp;&nbsp;&nbsp; <i>JOSTLE_THRESHOLD</i></td>

<td>Threshold at which the graph contraction phase is stopped. (integer)</td>
</tr>

<tr>
<td VALIGN=TOP>&nbsp;&nbsp;&nbsp; <i>JOSTLE_GATHER_THRESHOLD</i></td>

<td>Duplicate coarse graph on all processors when there are fewer than
this number of nodes. (integer)</td>
</tr>

<tr>
<td VALIGN=TOP>&nbsp;&nbsp;&nbsp; <i>JOSTLE_MATCHING</i></td>

<td>Matching algorithm for graph contraction. (Valid values are "local"
and "global".)</td>
</tr>

<tr VALIGN=TOP NOSAVE>
<td>&nbsp;&nbsp;&nbsp; <i>JOSTLE_REDUCTION</i></td>

<td NOSAVE>When reduction is turned off, Jostle performs a diffusion-type
algorithm instead of multilevel graph partitioning. (Valid values are "on"
and "off".)</td>
</tr>

<tr>
<td VALIGN=TOP>&nbsp;&nbsp;&nbsp; <i>JOSTLE_CONNECT</i></td>

<td>Make a disconnected graph connected before partitioning. (Valid values
are "on" and "off".)</td>
</tr>

<tr VALIGN=TOP NOSAVE>
<td>&nbsp;&nbsp;&nbsp; <i>CHECK_GRAPH</i></td>

<td NOSAVE>Level of error checking for graph input: 0 = no checking, 1
= on-processor checking, 2 = full checking.  (CHECK_GRAPH==2 is very slow and should
be used only during debugging).</td>
</tr>

<tr VALIGN=TOP NOSAVE>
<td>&nbsp;&nbsp;&nbsp; <i>SCATTER_GRAPH</i></td>

<td NOSAVE>Scatter graph data by distributing contiguous chunks of objects
(vertices)&nbsp; of roughly equal size to each processor before calling
the partitioner.  0 = don't scatter; 1 = scatter only if all objects are
on a single processor; 2 = scatter if at least one processor owns no objects;&nbsp;
3 = always scatter.&nbsp;</td>
</tr>

<tr>
<td VALIGN=TOP><b>Default values:</b></td>

<td>See the <a href="https://staffweb.cms.gre.ac.uk/~c.walshaw/jostle/">Jostle</a>&nbsp; documentation.&nbsp;
See our <a href="ug_alg_parmetis.html">ParMETIS section </a>for the last
two parameters.</td>
</tr>

<tr>
<td VALIGN=TOP><b>Required Query Functions:</b></td>

<td></td>
</tr>

<tr>
<td></td>

<td><b><a href="ug_query_lb.html#ZOLTAN_NUM_OBJ_FN">ZOLTAN_NUM_OBJ_FN</a></b></td>
</tr>

<tr>
<td></td>

<td><b><a href="ug_query_lb.html#ZOLTAN_OBJ_LIST_FN">ZOLTAN_OBJ_LIST_FN</a></b>
</td>
</tr>

<tr VALIGN=TOP NOSAVE>
<td></td>

<td NOSAVE>
<b><a href="ug_query_lb.html#ZOLTAN_NUM_EDGES_MULTI_FN">ZOLTAN_NUM_EDGES_MULTI_FN</a></b> or
<b><a href="ug_query_lb.html#ZOLTAN_NUM_EDGES_FN">ZOLTAN_NUM_EDGES_FN</a></b>
<br>
<b><a href="ug_query_lb.html#ZOLTAN_EDGE_LIST_MULTI_FN">ZOLTAN_EDGE_LIST_MULTI_FN</a></b> or
<b><a href="ug_query_lb.html#ZOLTAN_EDGE_LIST_FN">ZOLTAN_EDGE_LIST_FN</a></b>
</td>
</tr>
</table>

<p>
<hr WIDTH="100%">[<a href="ug.html">Table of Contents</a>&nbsp; | <a href="ug_alg_hier.html">Next:&nbsp;
Hybrid Hierarchical Partitioning</a>&nbsp; |&nbsp; <a href="ug_alg_parmetis.html">Previous:&nbsp;
ParMETIS</a>&nbsp; |&nbsp; <a href="https://www.sandia.gov/general/privacy-security/index.html">Privacy and Security</a>]
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